Upgrading From Millenium Edition To XP

I have upgraded my desktop computer from Millennium Edition to Windows XP Home Edition. I am now about to reinstall the XP OS again, to prepare for installation of DSL on my computer.My computer is a Compaq Presario (5000 series), 930 mhz processor, 128 mb ram, (soon to 500 mb), with previous Millennium Edition. I currently have a dial up connection and about to install DSL. The programs that I install on my computer are very minimal. Sometimes installing with or without McAfee, and, as alternative, installing AVG anti virus and the XP firewall. I don't install MS Works (the MS generic for WORD, the word processor), only using Word pad and Notepad. Adaware and sometimes Spybot. The third party programs are very few, like Roxio and the big programs are sometimes Nero and Photoshop. The immediate results from completing this installation this past summer, and on repeated re installations, were very much unsatisfactory.The main thing I remember, is that the computer's response was extremely slow in opening programs, slow response when clicking anything in an opened program, and very slow response in opening internet browsers and clicking links in browsers. My first actions to resolve the problems were to reinstall XP again and again by several ways: first installing my old ME CD (which was the Quickstore CD) and then XP over it then reinstalling XP in other ways, another time reinstalling by installing the XP CD of my laptop onto this desktop and my XP upgrade CD over it, and another time reinstalling it directly from an erased hard disk to the upgrade CD. I reinstalled the OS using combination of the above, to no avail.I had put aside figuring out the problem with this computer by using my computer's task manager to place high priority on the program I have open, and using only one program at a time. I am ugrading it to 512 mb soon. So, I hope that alleviates some of the problem of the slow response.Also, I have been using Drive Scrubber2 to erase the hard drive before reinstalling the operating system. I have scrubbed the HD at different levels, once absolutely thorough, requiring 24 hours. There shouldn't be any viruses on the computer. If Windows had required the presence of drivers on the HD that it writes over with re installation, then that could be the problem.